The invention relates to a diaphragm valve, in particular for fluid media, having a valve body, a diaphragm and a connecting piece actuatable by a drive unit for operating the diaphragm, wherein the valve body and the diaphragm are made of plastic.
Diaphragm valves having a valve body with an inflow and an outflow (DE 20 2005 002 152 U1) are known in the art. Furthermore, the valve bodies have a valve seat that can be sealed by a diaphragm, wherein the diaphragm is connected via a connecting piece with a pressure piece of a drive unit.
In a conventional diaphragm valve, the diaphragm is clamped during assembly between the drive unit or an intermediate piece, on the one hand, and the valve body, on the other hand. In this case, both the drive unit or the intermediate piece and the valve body may have a so-called QHD sealing contour.
WO 2010/025 905 A1 describes a single-layer diaphragm, which can also be integrally formed with the connecting piece or which can be formed on the connecting piece. The diaphragm is made of the same plastic material as the valve body, for example of polyethylene (PE) or polypropylene (PP). In addition, the valve body and the diaphragm are fixedly connected to each other by ultrasonic welding to form a fluid-tight valve body unit which can be coupled with the drive unit.
The fixed connection between the valve body and the diaphragm to form a sealed valve body unit allows to form the valve body unit as a disposable unit, and to integrate the diaphragm valve into a disposable tube system or a pre-sterilizable pharmaceutical facility. The valve body unit can therefore be formed inexpensively as a disposable or single-use valve body unit and coupled or connected to a reusable drive unit. The valve body unit is sealed during the transport phase by the fixed connection of the diaphragm and the valve body. Contamination of the valve chamber and the environment is thus avoided. However, it has been observed that the welding of the diaphragm and the valve body, particularly when using ultrasound, generates abraded particles intrinsic to the process. These abraded particles can no longer be flushed out of the valve after the welding. However, the abraded particles could be detected as a residue in the liquid and/or gas stream flowing through the valve even when the valve is used as intended.